Trouble Shooting Crate V1512 - Help Please!

[PeaceMaker]

Hi All,


Glad to see you are all still here.


I have a Crate V1512 that I'm having some trouble with and it all started when I tried using "Carl's Custom Guitars Speaker Soak" on it... It started out working pretty good but then I started to get a strange anomaly... Now with the Speaker Soak off/removed and the gain and level turned all the way to zero it still lets the guitar signal through... To put it another way, I can turn the amp all the way down to zero and use my thumb to tap the end of the guitar cable jack and the signal goes through when the amp should be dead quiet... Have any idea what is causing this?


Thanks for all you help,
PeaceMaker   

[silverfox]

It is not likely that something malfunctioning on the output, which is where the speaker soaker was located, would cause a problem in the preamp section. I suspect the problem either was already present or developed coincidentally but unrelated to the use of the soaker. In looking at the schematic it doesn't appear that could have caused a problem. Something to check however would be the impedance setting for the soaker. How many ohms? The schematic indicates a 16 ohm speaker load for test purposes.

The method of testing also is not going to provide a good basis. If you have a different signal source such as a cd player and adapter jack that may provide you with a better source. Short of all that your going to have to make some checks based on the schematic attached; if that's something your comfortable trying.

silverfox.

[PeaceMaker]

Hi silverfox, and thanks.


Here's a link to the Speaker Soak I purchased: http://carlscustomguitars.com/Speaker-Soak-true-power-tube-guitar-amp-volume-attenuator-Speaker-Soak.htm?productId=17 ... I got the 16 ohm version and it goes between the speaker out and speaker.


Another thing the Crate v1512 does is when everything was working right I would set the level and volume to 3 and I would get a nice clean tone (and with a tube screamer it would be about perfect) but now at 3 it gives me a whole lot of hiss so much so that I can't use it there anymore (with or without the screamer); but if I turn it up higher to about 5 or 6 (it varies) the hiss goes away... Any ideas? Could the tubes need replaceing? Maybe the pots (it has plastic pots)?


Also not very skilled at tube amp I can't read a schematic... About the only thing I've done is changed tubes and speaker... I can solder pretty well done some guitar work and pedal mods... Maybe with help I could do a replace/repair.

[mresistor]

It sounds to me like the GAIN pot  (250K) could be dirty/bad. I can't see your amp, and I don't have one. But sometimes there is an opening on potentiometers  that allow you to apply some contact cleaner to the inside resistive surface (usually carbon)  and contacts and clean it.  The opening is usually in the area of where the leads are. Your pots have plastic shafts, the case where the innards are is usually metal. The amp cover needs to be removed to check the pot out. It could be a job that might be beyond your expertise and I don't know your location but if you have a music store someone there should be able to recommend an amp tech. If you need a new pot you might have to pull the whole circuit board up to access the solder pads, and that can be tricky on these mass produced units.

[PeaceMaker]

Thanks mresistor,


 I do have some deoxit that I can squirt in there (soon as I get some time and can get to them)... Also if I replace the pots how would I know what size and value to get and where to get them?... The shafts on them are really small in diameter and look cheaply made.


Also, if I have to take it to a tech you have any idea how much it would take to fix it (just a guesstamation)?


And here's the Users Manual: http://www.crateamps.com/pdf/manuals/V1512.pdf .

Anyone else have any ideas or advice?


Thank you.


 


 

[shooter]

zero it still lets the guitar signal through...

how *much* signal, like you're dimed, rocking on stage?, or just some minor, wow, I still hear my guitar?
do all the knobs still do what they should otherwise?
EDIT: if you have Nothing plugged in and amp turned to Zero, what do you hear?

how much

I charge an hourly rate, + parts, what's the amp worth, how much do you want to put into it, then you call a tech, most are pretty reasonable folk

[PeaceMaker]

Hi shooter and thanks.

Now with... the gain and level turned all the way to zero it still lets the guitar signal through... To put it another way, I can turn the amp all the way down to zero [both gain and level down to zero] and use my thumb to tap the end of the guitar cable jack and the signal goes through when the amp should be dead quiet.

It's not loud it just sounds like it's turned up a couple notches above the noise floor... When I touch the guitar cable jack the end that plugs into the guitar I get like static jip-jip sound... You know you've done it before: just turn your amp down low pull the plug out of you guitar and touch the tip of the jack and you can tell a signal is going through... Only with my amp the signal is going through when both the gain and level are in the off position.

I just want it repaired to the way it was working I think they cost about $300.00 used now.


Any ideas? Anybody?

[mresistor]

The part number should be stamped into the metal case somewhere or it could be printed on it. It is a PC board mount pot and it will likely look like one of these.  https://www.tubesandmore.com/products/potentiometers_0?filters=Application%3DAmp%2CValue/Size%3D16mm%20Body%2CResistance%3D250k  but there are many more say at mouser.com.
I can't say what it would cost without having it in front of me. Or if you need a new pot.


here is another one  http://newoldsounds.com/general/529-16mm-pc-mount-potentiometer-250k-logaudio.html


another source   http://www.amprepairparts.com/pots.htm




Looking at the PCB diagram Silverfox so generously provided, it looks like you just need a 250K PCB mount with the leads coming straight down , three in a row   
something similar to this

[Paul1453]

how much

I charge an hourly rate, + parts, what's the amp worth, how much do you want to put into it, then you call a tech, most are pretty reasonable folk

Some places charge like $20-$40, the tech's hourly rate, to write you up a detailed estimate of parts and labor costs needed to repair the amp.
Most will apply that estimate charge to the labor quoted if you have them fix your amp.  Negotiate this beforehand.
If not you can take the detailed estimate, purchase the parts and try to do the repairs yourself.
That is one way to get the problem troubleshot for you if you're not good with schematics yet. 

[PeaceMaker]

Thanks mresistor and Paul1453 for all the time/work you put in to help me (things are getting clearer)... I have yet to get my amp on the work bench to take a look at it (soon I hope).


Also I was wondering if maybe something else other than the pots could be the problem?... Like I was wondering if maybe the speaker soak put some extra strain on one of the components like maybe a resister or capacitor blew; or maybe a tube was damaged (sorry if these are stupid questions- I know very little about tube amps).


Anyone else, have a theory? 

[mresistor]

As silverfox has stated it is "highly unlikely there is a problem in your power amp section", because if you used a power soak that was the correct impedance for the amps output there is no reason to suspect a problem there. Your description of the problem seems to relate to the preamp section. The pots in some of these mass produced units are very cheap in quality and since you use the gain/level pots all the time they get a lot of use.

[shooter]

As shooter has stated

Silerfox get the credit for that statement, but I do 2nd him

[mresistor]

OOOPs    thanks Shooter .

[PeaceMaker]

Thanks silverfox, mresistor, shooter, Paul1453, and all for all your help and expertise... I guess it's up to me now (or a tech); I'll let you know how it goes as soon as I can get to it.

Thanks again; and take care,
Peacemaker

P.S. If anyone would like to add to this thread feel free... All input appreciated. :)